The present invention relates to printed circuit board systems of the type having a mainboard (also known as a motherboard) into which one or more printed circuit boards (known as expansion cards or daughterboards) are connected via connector arrangements and, more particularly, to an enclosure system for the expansion cards that provides a ruggedized containment for each expansion card and which maximizes the opportunity for heat transfer from the expansion card to the external environment and which also provides improved EMI shielding.
In the packaging of electronic systems using a plurality of printed circuit boards, one common architecture involves a primary printed circuit board, variously referred to as a backplane, a baseboard, a mainboard, or, more commonly, as a motherboard, that includes a plurality of connectors for receiving subsidiary printed circuit boards, commonly referred as expansion cards or daughterboards. With this type of system, currently used in personal computers, function-specific expansion cards can be easily removed and replaced with different expansion cards having improved functionality or different functions. Typically, the expansion cards correspond to one of several form factors and have standardized edge connectors: expansion cards in common usage can conform to the ISA, EISA, AGP, PCI, PCIe standards and variants thereof with the expectation that expansion card form-factors and connector arrangements will continue to evolve.
In the motherboard/expansion card architecture discussed above and as used in many computer architectures, the expansion cards are typically held in place by a single threaded fastener at one end of the expansion card, and/or, in some cases, by claw-like clamp at the opposite ends of each expansion card that interengages with the connector. While these board-retaining arrangements are adequate for stationary applications with a minimum of vibration, the generic motherboard/expansion card architecture is not well suited for mobile applications where the system will be exposed to vibrations, shock forces, jolts, and other accelerations or G-forces. Additionally, the individual expansion cards in the generic motherboard/expansion card architecture are exposed to EMI radiated from adjacent expansion cards and from other EMI sources.
The heat generated by the electronic components in the motherboard/expansion card architecture is typically transferred from the boards by forced air cooling by which fan-forced ambient air passes over the boards to remove heat with the now-heated air exhausted from the enclosure. Typically, some types of enclosures contain the motherboard/expansion card assembly with one or more axial-flow fans mounted in the enclosure and, in many cases, smaller axial-flow fans and fan/heat sink combinations are attached to selected integrated circuits on the boards, these integrated circuits typically providing microprocessor, graphical, or video processing functionality.